The present application relates generally to semiconductor devices, and more specifically to conductive contacts for fin-type field effect transistors and their methods of fabrication.
Fully depleted devices such as fin field effect transistors (finFETs) are candidates for scaling of gate lengths to 14 nm and below. The manufacture of FinFETs typically leverages a self-aligned process to produce extremely thin fins, e.g., 20 nm wide or less, on the surface of a substrate using selective-etching techniques. A gate structure is then deposited to contact multiple surfaces of each fin to form a multi-gate architecture.
The narrow, three-dimensional fin geometry may be beneficial for electrostatic control the transistor channel, but can lead to increased contact resistance in the source/drain regions of the device. A larger contact area (and therefore less contact resistance) can be provided by merging the source/drain regions of adjacent fins, and the contact resistance may be decreased further by converting an upper portion of epitaxial junctions in the source/drain regions to a silicide.
In conventional FinFET structures, electrical contact to the source/drain region is typically made through a contact trench that extends through a dielectric layer. A conductive contact is formed within the trench. The conductive contact conventionally includes a fill metal such as tungsten and a liner/barrier layer between the fill metal and the dielectric walls of the trench.
One factor that contributes to the overall performance of such conductive contacts is the resistance contribution of the liner/barrier layers, which are incorporated into the structure to promote nucleation and adhesion of the fill metal layer and/or inhibit diffusion or segregation of the fill metal into adjacent structures, including the dielectric layer. However, as device architectures scale to smaller critical dimensions and higher densities, conventional liner/barrier layers can have an adverse effect on the total resistance through the conductive contact. It would therefore be beneficial to provide a conductive contact architecture having a minimal footprint and low overall resistance.